KR102116828B1 - Method of recycling a substrate - Google Patents

Abstract

A substrate regeneration method and a regeneration substrate are disclosed. This method prepares a substrate having a surface separated from the epi layer on the front surface, forms a protective film on the back surface of the substrate, etches the surface of the substrate using electrochemical etching technology, and etched the surface using electrochemical etching technology. And etching using a chemical formula technique. Accordingly, the substrate can be regenerated to have a good growth surface, and it is possible to prevent the back surface of the substrate from being damaged during electrochemical etching or chemical etching.

Description

Substrate regeneration method {METHOD OF RECYCLING A SUBSTRATE}

The present invention relates to a method for regenerating a substrate, and more particularly, to a method for regenerating a growth substrate separated from a nitride-based epi layer.

After growing an epi layer on a substrate, a technique of separating the substrate from the epi layer is used. For example, a gallium nitride-based vertical light emitting diode may be manufactured by growing an epi layer including n-type and p-type semiconductor layers on a growth substrate, and then separating the growth substrate. The luminous efficiency can be improved by attaching a supporting substrate having a higher thermal conductivity than the growth substrate to the epi layer.

As described above, a technique of using a growth substrate for epi layer growth, and then attaching the growth substrate and other support substrates to the epi layer in consideration of the operating characteristics of the device, and separating the growth substrate from the epi layer can be used. . The growth substrate may be separated into an epitaxial layer using techniques such as laser lift off, chemical lift off, or lift off using thermal or mechanical stress.

At this time, the separated growth substrate can be reused as a substrate for growing the epi layer, and thus, the manufacturing cost of the substrate can be reduced.

However, in order to reuse the substrate separated from the epi layer, the separated surface must be treated flat. For this, it is generally possible to think of chemical mechanical polishing methods. However, since the substrate used for growing the gallium nitride-based semiconductor layer or the gallium nitride-based semiconductor layer grown thereon is relatively high in hardness, it is very difficult to make the surface flat using a chemical mechanical polishing method. Accordingly, the surface polished by chemical mechanical polishing includes many scratches, and further cracks may be generated.

Moreover, when the gallium nitride-based semiconductor layer remains on the initial substrate used as the growth substrate, the remaining gallium nitride-based semiconductor layer is fragile by chemical mechanical polishing, making it difficult to find suitable process conditions.

Meanwhile, a technique of completely removing the gallium nitride-based semiconductor layer remaining on the substrate by heating and decomposing it may be used. However, it is expensive to remove the already grown gallium nitride-based semiconductor layer by heating at a high cost, and furthermore, it may be difficult to apply because certain conditions, for example, when the initial substrate is a gallium nitride substrate, may damage the initial substrate.

The problem to be solved by the present invention is to provide an improved substrate recycling method capable of recycling the substrate.

Another problem to be solved by the present invention is to provide a substrate regeneration method capable of regenerating the substrate without damaging the initial growth substrate.

A substrate regeneration method according to an aspect of the present invention includes preparing a substrate having a surface separated from an epi layer on the front surface; Forming a protective film on the back side of the substrate; Etching the surface of the substrate using an electrochemical etching technique; And etching the surface etched using the electrochemical etching technique using the chemical etching technique.

The surface separated from the epi layer can be planarized by using the electrochemical etching and chemical angle together, and thus the substrate separated from the epi layer can be reused as a growth substrate for epi layer growth. Furthermore, by forming a protective film on the back side of the substrate, it is possible to prevent the back side of the substrate from being damaged during electrochemical etching or chemical formula angle.

The protective film may include a SiO ₂ layer, a Kepton tape, or a thermal tape. When the protective film is a SiO ₂ layer, the protective film may be formed to a thickness within a range of 5000 mm to 5 μm. In addition, the protective film may be formed to cover the side surface of the substrate. For example, by exposing the substrate side during the deposition of the SiO _2, it may be SiO ₂ is deposited on the substrate side. Accordingly, the side surface of the substrate may be protected during electrochemical etching or chemical etching. The protective layer is removed after the chemical formula ends.

The substrate having the separated surface may have a sacrificial layer on the surface. The sacrificial layer may include an n-type gallium nitride-based semiconductor layer. Furthermore, the substrate having the separated surface may further include an etch stop layer under the sacrificial layer. The etch stop layer may include an undoped gallium nitride-based semiconductor layer. Fine pores may be formed in the sacrificial layer by the electrochemical etching. In addition, the sacrificial layer is etched and removed by the chemical etching, and the etch stop layer is exposed. The etch stop layer is resistant to electrochemical etching and also stops etching by chemical etching.

On the other hand, the separated surface includes a protrusion and a recess, and the protrusion may have a relatively flat surface compared to the recess. The protrusion may be formed in a stripe shape, an island shape, or a mesh shape. The protrusions and recesses may be formed when the substrate is separated from the epi layer using a chemical lift-off technique.

The substrate having the separated surface may include an initial substrate. The initial substrate is a substrate for growing a gallium nitride-based semiconductor layer, and may be a sapphire substrate or a gallium nitride substrate.

Meanwhile, the electrochemical etching may be performed by applying a voltage of 20 to 60V using an oxalic acid solution. In addition, the chemical formula angle may be performed using a solution containing NaOH or KOH.

A substrate regeneration method according to another aspect of the present invention provides a substrate having a relatively flat surface and a surface having a relatively rough surface regularly aligned; Etching the surface of the substrate using an electrochemical etching technique; And etching the surface etched using the electrochemical etching technique using the chemical etching technique.

The flat surface may be arranged in a stripe shape, island shape or mesh shape.

Furthermore, the substrate surface may be the surface of the n-type gallium nitride-based semiconductor layer. Further, the substrate may further include an undoped gallium nitride-based semiconductor layer under the n-type gallium nitride-based semiconductor layer.

According to another aspect of the present invention, a method for regenerating a substrate includes preparing a substrate including an n-type gallium nitride-based semiconductor layer on an upper surface; Forming a protective film on the back side of the substrate; Etching the n-type gallium nitride based semiconductor layer using an electrochemical etching technique; And etching the n-type gallium nitride based semiconductor layer etched using the electrochemical etching technique using a chemical etching technique.

The substrate may further include an undoped gallium nitride-based semiconductor layer located under the n-type gallium nitride-based semiconductor layer, and the undoped gallium nitride-based semiconductor layer is exposed by the chemical angle.

The undoped gallium nitride-based semiconductor layer may function as an etch stop layer for electrochemical etching while etching the n-type gallium nitride-based semiconductor layer by using electrochemical etching. Therefore, it is possible to prevent the initial substrate surface under the undoped gallium nitride-based semiconductor layer from being damaged by electrochemical etching or chemical etching.

The n-type gallium nitride-based semiconductor layer may include a flat surface and a rough surface, and the flat surface may protrude above the rough surface.

Meanwhile, the protective layer may be formed to cover the side surface of the substrate. In addition, the protective film may be formed of SiO ₂ , 켑 ton tape or thermal tape.

According to embodiments of the present invention, it is possible to provide a regenerated substrate suitable for growing a gallium nitride-based semiconductor layer having a relatively flat surface. Furthermore, it is possible to provide a regenerated substrate including an undoped gallium nitride-based semiconductor layer on top.

1 to 3 are cross-sectional views illustrating a method of manufacturing a light emitting diode using a growth substrate separation technology according to an embodiment.
4 to 6 are plan views for explaining a mask pattern used to separate the growth substrate.
7 is a cross-sectional view for explaining the substrate separated from the epi layer.
8 is a planar SEM image showing the surface of the substrate separated from the epi layer.
9 is a schematic process flow chart for explaining a method for regenerating a substrate according to an embodiment of the present invention.
10 is a schematic cross-sectional view for explaining etching the surface of a substrate using an electrochemical etching technique according to an embodiment of the present invention.
11 is a planar SEM image after etching a substrate surface using an electrochemical etching technique.
12 is a schematic cross-sectional view for explaining etching of a surface of a substrate using a chemical etching technique.
13 is a planar SEM image after etching the surface of the substrate using a chemical formula technique.
14 is an optical photograph showing the surface of a gallium nitride layer grown on a reproduction substrate.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided as examples to ensure that the spirit of the present invention is sufficiently conveyed to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. In addition, in the drawings, the same reference numbers indicate the same components, and the width, length, and thickness of the components may be exaggerated for convenience.

Embodiments of the present invention include growing a nitride semiconductor layer (epi layer) on a growth substrate, and then separating the growth substrate from the epi layer to provide a separated substrate. The epi layer separated from the growth substrate may be used to manufacture a semiconductor device such as a light emitting diode. Here, a technique for manufacturing a light emitting diode by separating a growth substrate is first introduced, and then a method for regenerating the separated substrate is described.

(Method for manufacturing light emitting diodes)

1 to 3 are cross-sectional views illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.

First, referring to Figure 1 (a), the growth substrate 110 is prepared. The growth substrate 110 may be a sapphire substrate, a GaN substrate, a silicon carbide (SiC) substrate, a silicon (Si) substrate, or the like. In particular, the growth substrate 110 may be a sapphire substrate or a GaN substrate, and may be polar, non-polar, or semi- It may include a polar substrate.

The etch stop layer 120 and the sacrificial layer 125 are formed on the growth substrate 110. The etch-stop layer 120 may include an undoped gallium nitride-based semiconductor layer, for example, undoped GaN, and the sacrificial layer 125 may include an n-type gallium nitride-based semiconductor layer 120. The undoped gallium nitride-based semiconductor layer 120 and the n-type gallium nitride-based semiconductor layer 125 are formed on the growth substrate 110 using, for example, techniques such as metalorganic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). Can be grown. The undoped gallium nitride-based semiconductor layer 120 is grown without intentional doping, and the n-type gallium nitride-based semiconductor layer 125 has a relatively high impurity concentration such as 1E17 to 1E19 / cm ³ Si doped gallium nitride. System, for example, a GaN layer. The nitride-based semiconductor layers described below may be grown using MOCVD or MBE technology, such as the undoped gallium nitride-based semiconductor layer 120 and the n-type gallium nitride-based semiconductor layer 125. No mention.

Referring to FIG. 1B, a mask pattern 130 is formed on the sacrificial layer 125. The mask pattern 130 may be formed of, for example, SiN or SiO ₂ to a thickness within a range of about 5 nm to 10 μm. In the mask pattern 130, as shown in FIG. 4 (a), each mask region may have a stripe shape, and as shown in FIG. 4 (b), shapes extending in different directions cross each other. Can have Alternatively, the mask pattern 130 is an embossed pattern, and as shown in FIG. 5 (a), the mask area may have a hexagonal shape, or as shown in FIG. 6 (a), the mask area It can have a rhombus shape. Alternatively, the mask pattern 130 is an intaglio pattern, and as shown in FIG. 5 (b), the opening area may have a hexagonal shape, or as shown in FIG. 6 (b), the opening area It can have a rhombus shape. The mask pattern 130 may also be an embossed pattern in which the mask area is circular, or an intaglio pattern in which the opening area is circular. The size of the regular pattern of the mask pattern 130 may be in the range of about 5 nm to 20 μm.

Referring to FIG. 1 (c), the micropores 150 are formed in the sacrificial layer 125 by partially etching the sacrificial layer 125 using electrochemical etching (ECE).

In the electrochemical etching process, the growth substrate 110 on which the sacrificial layer 125 is formed and the cathode electrode (eg, Pt electrode) are immersed in the ECE solution, and then a positive voltage is applied to the sacrificial layer 125 and the cathode electrode is negative. It is performed by applying a voltage of, and it is possible to control the size of the fine pores 150 by adjusting the molar concentration, the process time and the applied voltage of the ECE solution.

The ECE solution may be an electrolyte solution, for example, an electrolyte solution containing oxalic acid, HF or NaOH.

In this embodiment, the sacrificial layer 125 may be partially etched by one-step electrochemical etching (ECE) to continuously apply the same voltage, for example, a voltage in the range of 10 to 60V. However, the present invention is not limited thereto, and may be partially etched by a two-step electrochemical etching (ECE) method of initially applying a relatively low voltage and then applying a relatively high voltage. 1 (c) shows micropores 152 and 154 formed by two-step electrochemical etching, and micropores 152 are formed in a first step of applying a relatively low voltage, and relatively large micropores 154 is formed in two steps of applying a relatively high voltage. For example, for an n-type gallium nitride based semiconductor layer 125 having a Si doping concentration of 6E18 / cm ³ using a 0.3M oxalic acid solution at 20 ° C., step 1 applies a voltage of 8 to 9 V, 2 In the step, electrochemical etching may be performed by applying a voltage of 15 to 17V.

By using a two-step electrochemical etching, the surface of the n-type gallium nitride-based semiconductor layer 125 can maintain relatively good crystallinity, and also, is relatively large in the n-type gallium nitride-based semiconductor layer 125. The fine pores 154 can be formed, which is advantageous for a subsequent process.

Referring to FIG. 1 (d), epitaxial layers such as the first nitride semiconductor layer 160, the active layer 170, and the second nitride semiconductor layer 180 are used as the n-type gallium nitride-based semiconductor layer 125 as a seed. A nitride semiconductor stacked structure 200 including layers is grown. The nitride semiconductor stacked structure 200 covers the sacrificial layer 125 as well as the mask pattern 130 by horizontal growth.

The first nitride semiconductor layer 160 may be a single layer, but is not limited thereto, and may be a multiple layer. Such a multi-layer may include an undoped layer and a doped layer.

On the other hand, while the semiconductor stacked structure 200 is grown, the micropores 152 and 154 merge with each other and grow to form a cavity 150a. The cavity 150a is formed to connect adjacent mask regions of the mask pattern 130 to each other. In FIG. 1 (d), although the interface between the sacrificial layer 125 and the first nitride semiconductor layer 160 is shown to remain, the cavity 150a has the sacrificial layer 125 and the first nitride semiconductor layer ( 160).

Referring to FIG. 2 (a), a nitride semiconductor stacked structure 200 including a first nitride semiconductor layer 160, an active layer 170, and a second nitride semiconductor layer 180 is formed on the sacrificial layer 125. It is. As described above, while forming the semiconductor stacked structure 200, a cavity 150a is formed in the n-type gallium nitride based semiconductor layer 125 by the micropores 152 and 154 in the sacrificial layer 125. do. Here, FIG. 2 (a) shows the same process steps as FIG. 1 (d), and is simply expressed by different scales.

The first nitride semiconductor layer 160 is a nitride semiconductor layer doped with an impurity of a first conductivity type, for example, a III-N-based compound semiconductor doped with n-type impurities, such as (Al, In, Ga) N-based nitride It may be formed of a semiconductor layer, it may include a gallium nitride layer. Also, the first nitride semiconductor layer 160 may include an undoped layer in which impurities are not intentionally doped.

The active layer 170 may be formed of a III-N-based compound semiconductor, for example, a (Al, Ga, In) N semiconductor layer, and a single quantum well structure or a well layer (not shown) and a barrier layer (not shown) alternately It may be a multi-quantum well structure stacked with.

The second nitride semiconductor layer 180 includes a III-N-based compound semiconductor doped with a second conductivity-type impurity, eg, a P-type impurity, such as a (Al, Ga, In) N-based group III nitride semiconductor layer. And, for example, may include a GaN layer.

Referring to FIG. 2 (b), the isolation region 200a may be formed by patterning the nitride semiconductor stacked structure 200. The device isolation region 200a may be formed using a photo and etch process. A plurality of nitride semiconductor stacked structures 200 separated into individual device regions by the device isolation region 200a may be formed.

Meanwhile, as illustrated, the sacrificial layer 125 and the mask pattern 130 are exposed by the device isolation region 200a.

Referring to FIG. 2 (c), the supporting substrate 210 is attached on the nitride semiconductor stacked structure 200. The support substrate 210 may be bonded to the nitride semiconductor stacked structure 200 through the metal layer 190. The metal layer 190 may include, for example, a reflective metal layer 192, a barrier metal layer 194 and a bonding metal layer 196. The barrier metal layer 194 covers the reflective metal layer 192, and the bonding metal layer 196 surrounds them to protect the reflective metal layer 192 and the barrier metal layer 194 from etching solutions. The reflective metal layer 192 is electrically connected to the second nitride semiconductor layer 180.

In this embodiment, the metal layer 190 is described as being formed after forming the device isolation region 200a, but is not limited thereto. That is, the reflective metal layer 192 and the barrier metal layer 194 may be formed before forming the device isolation region 200a. Furthermore, the bonding metal layer 196 may also be formed before forming the device isolation region 200a.

Meanwhile, the support substrate 210 may have through holes 210a as illustrated. Although not particularly limited, these through holes 210a may be arranged to be located in the device isolation region 200a. For example, through holes 210a may be positioned near four corners of the nitride semiconductor stacked structure 200 positioned in one device region. The through holes 210a help the etching solution penetrate into the device isolation region 200a during chemical etching performed for chemical lift off (CLO), thereby shortening the time for separating the growth substrate 110.

Referring to FIG. 2 (c) again, the support substrate 210 may be a sapphire substrate, a GaN substrate, a glass substrate, a silicon carbide substrate or a silicon substrate, a conductive substrate made of a metallic material, or a circuit such as a PCB. It may be a substrate or a ceramic substrate.

In addition, a bonding metal layer (not shown) corresponding to the bonding metal layer 196 is provided on the support substrate 210 side, and a bonding metal layer on the support substrate 210 side and a bonding metal layer on the nitride semiconductor laminate structure 200 side The support substrate 210 may be attached to the nitride semiconductor stacked structure 200 by eutectic bonding (196).

Referring to Figure 2 (d), after the support substrate 210 is attached, an etching solution such as NaOH, BOE or HF The growth substrate 110 is separated from the semiconductor stacked structure 200 by a chemical formula angle. The etching solution may etch the mask pattern 130 or etch GaN at the interface between the mask pattern 130 and the nitride semiconductor stacked structure 200 to separate the growth substrate 110 from the nitride semiconductor stacked structure 200. . The etch stop layer 120 and the sacrificial layer 125 may remain on the separated growth substrate 110, which will be described in detail later with reference to FIG. 7.

As the mask pattern 130 is removed, an uneven structure having a recess region 130a and a protruding region 160a is formed on the surface of the nitride semiconductor stacked structure 200, particularly the first nitride semiconductor layer 160.

In this embodiment, although the growth substrate 110 is separated by chemical etching, the growth substrate 110 may be separated from the nitride semiconductor stacked structure 200 using physical stress. For example, after the plurality of cavities 150a are formed, the growth substrate 110 and the nitride semiconductor stacked structure 200 may be separated by applying stress to the mask pattern 130.

FIG. 3 (a) is an inverted view of FIG. 2 (d) in which the growth substrate 110 is separated. Referring to FIG. 3 (a), after the growth substrate 110 is separated, the surface may be cleaned using hydrochloric acid or the like to remove Ga droplets. In addition, a part of the nitride semiconductor stacked structure 200 may be removed using dry etching to remove the high-resistance nitride semiconductor layer remaining on the surface side.

Referring to FIG. 3 (b), a roughened surface R may be formed on the surface of the nitride semiconductor stacked structure 200 using a photoelectric chemistry (PEC) etching technique or the like. The roughened surface R is formed on the bottom surface of the recessed area 130a and the surface of the projected area 160a. In addition to the recessed region 130a and the protruding region 160a, a rough surface R is formed, thereby improving the light extraction efficiency of light generated in the active layer 170.

Referring to FIG. 3 (c), an electrode 220 is formed on the nitride semiconductor stacked structure 200. The electrode 220 may have an electrode pad to which a wire can be connected, and an extension portion extending from the electrode pad. The electrode 220 is electrically connected to the first nitride semiconductor layer 160. On the other hand, when the support substrate 210 is conductive, the support substrate 210 may be electrically connected to the second nitride semiconductor layer 180 to function as an electrode, or a separate electrode under the support substrate 210 Pads may be further formed. When the support substrate 210 is insulating, the metal layer 190 may be extended to the outside to form an electrode pad.

An insulating layer (not shown) covering the nitride semiconductor stack structure 200 may be additionally formed before or after forming the electrode 220.

Referring to FIG. 3 (d), the support substrate 210 is divided into individual device units to complete a light emitting diode. The upper support substrate 210 may be divided by performing scribing along the device isolation region.

According to this embodiment, the growth substrate 110 can be separated without damaging the nitride semiconductor stacked structure 200. Moreover, since the growth substrate 110 is separated using the cavity 150a formed between the growth substrate 110 and the semiconductor stacked structure 200, the growth substrate 110 can be easily separated using physical stress or chemical etching. Can be.

Furthermore, by forming the through holes 210a together with the device isolation region, the penetration of the etching solution can be made faster to shorten the process time. Also, the separated growth substrate 110 can be used again as a growth substrate.

In the above, using a chemical lift off or a stress lift off has been described for separating a growth substrate and manufacturing a light emitting diode, the present invention is not limited to these substrate separation methods, and other possible substrate separation methods such as laser lift off May be applied.

(How to play the board)

Hereinafter, a method of regenerating the separated substrate using the substrate separation technology will be described.

7 is a cross-sectional view for explaining the separated substrate 300 through the above-described technique, and FIG. 8 is an SEM photograph showing the surface of the separated substrate through chemical lift-off.

7 and 8, the separated substrate 300 may include an etch stop layer 120 and a sacrificial layer 125. The separated substrate 300 surface may include a protrusion 125a and a recess 125b, and the protrusion 125a has a relatively flat surface compared to the recess 125b. As shown in Fig. 8, the concave portion 125b has a very rough surface. Thus, a relatively flat surface protrudes upward compared to a relatively rough surface.

In this embodiment, the protrusion 125a corresponds to the masking area of the mask pattern 130, and the recess 125b corresponds to the cavity 150a. Accordingly, the protrusion 125a or the flat surface may be arranged in a regular shape, such as a stripe shape, an island shape, or a mesh shape, such as the mask pattern 130. The protrusion 125a and the recess 125b are formed in the sacrificial layer 125. Furthermore, the etch-stop layer 120 may be exposed on the concave portion 125b.

As described above, the sacrificial layer 125 may include an n-type gallium nitride-based semiconductor layer, and the etch-stop layer 120 may include an undoped gallium nitride-based semiconductor layer. Thus, the separated substrate 300 may have an n-type gallium nitride-based semiconductor layer 125 on the surface, and the protrusions 125a and recesses 125b are formed on the n-type gallium nitride-based semiconductor layer 125 surface. Can be.

As shown in FIGS. 7 and 8, the separated substrate 300 has a very rough surface and can also have protrusions 125a and recesses 125b. Such rough surfaces are not limited to chemical lift off, but also occur in substrate separation technology through stress lift off (SOL) or laser lift off (LLO). In order to reuse the substrate having these rough surfaces as a growth substrate, a process for planarizing the surface is required.

Hereinafter, a method of reproducing the separated substrate will be described in detail.

9 is a schematic process flow chart for explaining a substrate regeneration method according to an embodiment of the present invention, and FIGS. 11 to 12 illustrate each process step of performing a substrate regeneration method according to an embodiment of the present invention These are the cross sections for.

Referring to FIG. 9, a separated substrate 300 as described above with reference to FIG. 7 is prepared (S100). The separated substrate 300 has an epi layer on the front surface, for example, a surface separated from the semiconductor stacked structure 200. The separated substrate 300 includes the initial substrate 110 and may include a sacrificial layer 125 and an etch-prevention layer 120 positioned below the sacrificial layer 125, as described with reference to FIG. 7. . The initial substrate 110 is a growth substrate for growing a gallium nitride-based semiconductor layer, for example, may be a sapphire substrate or a gallium nitride substrate, and may include a polar, non-polar, or semi-polar substrate.

9 and 10, a protective layer 210 is formed on the back side of the substrate 300 (S200). 10 (a) and 10 (b), the protective film 210 may be formed on the side surface of the substrate 300 as well as the back surface of the substrate 300. The passivation layer 210 may be formed of, for example, a SiO ₂ layer, a Kapton tape, or a thermal tape. SiO2 may be deposited on the back side of the substrate 300 using deposition equipment. At this time, by exposing the side surface of the substrate 300 to the outside, SiO ₂ particles deposited on the back surface of the substrate 300 are also deposited on the side surface to protect the side surface of the substrate 300.

In the case of the SiO ₂ layer, it was confirmed through experiments that the NaOH solution used for chemical etching was etched for about 600 mm 3 for 30 minutes and about 1500 mm for 1 hour. Therefore, the back surface and the side surface of the substrate 300 may be protected by allowing SiO ₂ or more to be deposited on the side surface of the substrate 300. However, when the surface roughness of the back surface of the substrate 300 is very poor, the thickness of the SiO ₂ layer may be 5000 kPa or more. The upper limit of the SiO ₂ layer is not particularly limited, but is preferably formed to a thickness of 5 μm or less in consideration of process time, material cost, and the like.

In this embodiment, the substrate 300 may be a GaN substrate, in particular, the back surface of the substrate 300 may be an N-face (N-face). The N-plane of GaN can be more easily damaged by the electrochemical etching or chemical formula than the Ga-plane. Therefore, the protective film 210 covers the N-plane of the substrate 300 to protect the N-plane in the electrochemical etching or chemical formula processes described later.

9 and 11, the surface of the separated substrate 300 is etched using electrochemical etching (ECE) technology (S300). Fine pores 252 may be formed in the upper region of the substrate 300, for example, the sacrificial layer 125 by electrochemical etching (ECE) technology. Meanwhile, the etch-stop layer 120 prevents micro-pores 252 from being formed on the surface of the initial substrate 110.

In the electrochemical etching (ECE) process, after dipping the separated substrate 300 and the cathode electrode (eg, Pt electrode) into the ECE solution, a positive voltage is applied to the sacrificial layer 125 and a negative voltage is applied to the cathode electrode. It is performed by applying, and it is possible to control the size of the fine pores 252 by adjusting the molar concentration, the process time and the applied voltage of the ECE solution. The ECE solution may be an electrolyte solution containing oxalic acid. For example, the electrochemical etching may be performed by applying a voltage in the range of 20-60V in the oxalic acid solution. The electrochemical etching is performed at a relatively high voltage, wherein the protective layer 210 protects the side and back surfaces of the substrate 300.

9 and 12, the surface of the separated substrate 300 is etched using a chemical etching technique (S400). The portion previously etched by electrochemical etching is removed by chemical etching, and a regeneration substrate 400 is provided. In this embodiment, the sacrificial layer 125 is removed by the chemical etching, and a regeneration substrate 400 in which the etch stop layer 120a remains may be provided. The etch-stop layer 120a may be an etch-stop layer 120 whose surface is etched by chemical etching. The higher the resistance of the etch stop layer 120 to the chemical etching, the more the surface etch is prevented.

The chemical etching may be performed, for example, in a solution containing NaOH or KOH. In addition, the solution may be heated to about 50 ℃ or more to help the etching.

On the other hand, the protective layer 210 prevents the side and back surfaces of the substrate 300 from being etched by the chemical etching.

9 and 13, the protective layer 210 is then removed (S500). When the protective layer 210 is a SiO2 layer, it may be removed using BOE. Accordingly, the regeneration substrate 400 for growing the gallium nitride-based epi layer is completed.

A gallium nitride-based semiconductor layer may be grown on the regeneration substrate 400. Furthermore, after the undoped gallium nitride-based semiconductor layer is additionally grown on the regenerated substrate 400 and the sacrificial layer 125 of the n-type gallium nitride-based semiconductor layer is further grown, it will be described with reference to FIGS. 1 to 3 above. A light emitting diode can be manufactured by applying the process as described above.

The method for regenerating a substrate according to the present exemplary embodiments can provide a regenerated substrate having a relatively flat surface by using electrochemical and chemical angles together. Furthermore, the substrate regeneration method does not need to remove all of the gallium nitride-based semiconductor layers grown on the initial substrate 110, and only some of the gallium nitride-based semiconductor layers on the surface are removed. Therefore, the material utilization efficiency can be increased as compared to the conventional technique of removing all of the semiconductor layers already grown, which is more suitable for substrate regeneration.

In addition, since the back and side surfaces of the substrate 110 are protected with a protective layer 210, it is possible to prevent the back or side surfaces of the substrate 110 from being damaged during electrochemical etching or chemical formula.

Although various embodiments have been described above, the present invention should not be understood as being limited to specific embodiments. In addition, the components described in the specific embodiments can be applied to other embodiments without departing from the technical spirit of the present invention.

Claims (22)

Preparing a substrate having a surface separated from the epi layer on the front surface;
Forming a protective film on the back side of the substrate;
Etching the separated surface of the substrate having the protective film using an electrochemical etching technique;
Etching the surface etched using the electrochemical etching technique using a chemical etching technique,
The substrate having the separated surface has a sacrificial layer positioned on the surface, and an etch stop layer positioned below the sacrificial layer,
The sacrificial layer includes an n-type gallium nitride based semiconductor layer, and the etch stop layer includes an undoped gallium nitride based semiconductor layer,
A substrate regeneration method in which the n-type gallium nitride based semiconductor layer is etched and removed by the chemical angle, and the undoped gallium nitride based semiconductor layer is exposed. Preparing a substrate having a surface separated from the epi layer on the front surface;
Forming a protective film on the back side of the substrate;
Etching the separated surface of the substrate having the protective film using an electrochemical etching technique;
Etching the surface etched using the electrochemical etching technique using a chemical etching technique,
The separated surface includes a protrusion and a recess, and the protrusion has a relatively flat surface compared to the recess. Preparing a substrate having a surface separated from the epi layer on the front surface;
Forming a protective film on the back side of the substrate;
Etching the separated surface of the substrate having the protective film using an electrochemical etching technique;
The surface etched using the electrochemical etching technique is etched using the chemical etching technique,
After etching using the chemical etching technique, the substrate regeneration method comprising removing the protective film. The method according to any one of claims 1 to 3,
The protective film is a substrate regeneration method comprising a SiO ₂ layer. The method according to claim 4,
The protective film is a substrate regeneration method that is formed to a thickness in the range of 5000Å to 5㎛. The method according to any one of claims 1 to 3,
The protective film is formed to cover the side surface of the substrate. The method according to claim 2 or 3, wherein the substrate having the separated surface has a sacrificial layer on the surface. The method of claim 7, wherein the substrate having the separated surface further comprises an etch stop layer under the sacrificial layer. The method of claim 8, wherein the sacrificial layer includes an n-type gallium nitride based semiconductor layer, and the etch stop layer comprises an undoped gallium nitride based semiconductor layer. The method of claim 9, wherein the n-type gallium nitride based semiconductor layer is etched and removed by the chemical formula, and the undoped gallium nitride based semiconductor layer is exposed. The method of claim 10, wherein micropores are formed in the n-type gallium nitride based semiconductor layer by the electrochemical etching. The method according to claim 1, wherein micropores are formed in the n-type gallium nitride based semiconductor layer by the electrochemical etching. The method according to claim 1 or 3, wherein the separated surface includes a protrusion and a recess, and the protrusion has a relatively flat surface compared to the recess. The method of claim 13, wherein the protrusion is formed in a stripe shape, an island shape, or a mesh shape. The method according to any one of claims 1 to 3, wherein the substrate having the separated surface includes an initial substrate, wherein the initial substrate is a gallium nitride substrate. The method according to any one of claims 1 to 3, wherein the electrochemical etching is performed by applying a voltage of 20 to 60 V using an oxalic acid solution. The method of claim 16, wherein the chemical formula is performed using a solution containing NaOH or KOH. The method according to claim 1 or claim 2,
After etching using the chemical etching technique, the substrate regeneration method comprising removing the protective film. Preparing a substrate including an n-type gallium nitride-based semiconductor layer on an upper surface;
Forming a protective film on the back side of the substrate;
Etching the n-type gallium nitride based semiconductor layer using an electrochemical etching technique;
And etching the n-type gallium nitride based semiconductor layer etched using the electrochemical etching technique using a chemical etching technique. The method according to claim 19, The substrate further comprises an undoped gallium nitride-based semiconductor layer located under the n-type gallium nitride-based semiconductor layer,
The undoped gallium nitride-based semiconductor layer is exposed to the substrate by the chemical formula. The method of claim 19, wherein the protective film is formed to cover a side surface of the substrate. The method of claim 21, wherein the protective film is formed of a SiO ₂ layer.

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